Retinal neovascularization can be produced in kittens exposed to elevated oxygen levels and then returned to room air. This forms the experimental animal model of the human condition of retrolental fibroplasia. It has been widely suggested that retinal ischemia induces a stimulus for the neovascularization of retrolental fibroplasia and other human neovascular diseases such as proliferative diabetic retinopathy. On-going research by other investigators in this laboratory has demonstrated a protein factor in the vitreous of animal and human eyes whose concentration parallels new vessel formation. The proposed research will involve developing techniques for repeated injections of this isolated angiogenesis factor into the vitreous of normal kittens, attempting to produce neovascularization.